File Access Using Counter Locking Mechanism

ABSTRACT

In an embodiment, a method is provided for accessing a file node. In this method, file access request specifying a file node to be accessed by way of a file system is received at a server from a client device. A counter is referenced to identify that the file node is being accessed in response to a different file access request. The counter is configured to track whether the file node is being accessed. The file node is provided to the client device when the counter indicates a termination of access to the file node resulting from the different file access request.

FIELD

The present disclosure relates generally to file access. In an exampleembodiment, the disclosure relates to network access to files by way ofa file system by a plurality of users.

BACKGROUND

Generally, a file system may be accessible over a network to one or moreusers. When a user requests access to the file, the file may beretrieved via the file system and provided to the user if the file isnot currently being accessed by another person. While the user isaccessing the file, the file may be locked such that other individualsare unable to write to the file.

However, if the file is currently being accessed by another person, thefile system server may determine that the file is locked and return anerror exception to the user indicating that the file is currently inuse. In this case, the user may be able to access a read-only copy ofthe file, and the server may return a copy of the last saved version ofthe file. However, if the user wishes to modify the file, the user mayneed to resubmit the request to access the file at a later time. Thismay require resubmitting the request several times until the filebecomes available, which may result in heavy traffic across the networkand at the server, as the server may need to process the request eachtime it is sent and return an error exception each time the requestcannot be processed.

BRIEF DESCRIPTION OF DRAWINGS

The present disclosure is illustrated by way of example and notlimitation in the figures of the accompanying drawings, in which likereferences indicate similar elements and in which:

FIG. 1 is a block diagram depicting an architectural overview of asystem for accessing files via a network, in accordance with an exampleembodiment;

FIG. 2 is a block diagram showing example components of a repositorymodule, in accordance with an example embodiment;

FIG. 3 is a flow diagram of a method of accessing a file node, inaccordance with an example embodiment;

FIG. 4 is a flow diagram of a method of reading a file, in accordancewith an example embodiment;

FIG. 5 is a flow diagram of a method of writing to a file, in accordancewith an example embodiment; and

FIG. 6 is a block diagram depicting a machine in the example form of acomputing device within which may be executed a set of instructions forcausing the machine to perform any one or more of the methodologiesdiscussed herein.

DETAILED DESCRIPTION

The description that follows includes illustrative systems, methods,techniques, instruction sequences, and computing machine programproducts that embody illustrative embodiments of the present technology.In the following description, for purposes of explanation, numerousspecific details are set forth in order to provide an understanding ofvarious embodiments of the inventive subject matter. It will be evident,however, to those skilled in the art, that embodiments of the inventivesubject matter may be practiced without these specific details. Ingeneral, well-known instruction instances, protocols, structures andtechniques have not been shown in detail.

Some embodiments described herein provide techniques for accessing filesor folders containing files at a server. Throughout the description,access to files may be described. However, the description of access tofiles may similarly be applied to any file node in a file system (e.g.,file system directories, etc.). For example, a repository module at theserver may receive from a client device a file access request specifyinga file to be accessed by way of a file system. A file access request mayinclude a request to read a file or a request to modify a file (e.g.,write to, delete, etc.). The repository module may determine whether thefile is currently being accessed in response to another file accessrequest by referencing a locking mechanism counter. If the repositorymodule identifies that the file is being accessed in response to theother file access request, the repository module may wait apredetermined amount of time and reference the counter again thereafter.When the counter indicates access to the file resulting from the otherfile access request has terminated, the file may be provided to theclient device.

When the file system server receives a file access request from a clientdevice, the request is held until the requested file becomes available.While the request is being held, the repository module of the serverreferences the locking mechanism counter to determine when the file canbe accessed. The locking mechanism counter keeps track of the number ofpeople reading and writing to a file and may be adjusted each time thefile is accessed and each time access to the file has terminated.

In some embodiments, the file access request may be a batch requestrequesting access to a plurality of files. If the batch request is arequest to read several files, the files may be returned to therequesting client device as each file becomes available, using thecounter associated with each file to determine when each file becomesavailable. If the batch request is a request to modify several files(e.g., add a file, delete a file, change a file, etc.), the repositoryserver may apply the write command to each file specified in the batchrequest as each file becomes available, using the counter associatedwith each file to determine when each file becomes available. Forexample, a file access request may request that a modification be madeto files stored within a folder or to a file which includes contentcontained in one or more other files. The batch request may result inmodification of those files as each of the files associated with thebatch request becomes available.

FIG. 1 is a block diagram depicting an architectural overview of asystem 100 for accessing files in a file system data repository 108 viaa network 110. In some embodiments, the networked system 100 may includeany number of client devices, such as client devices 112.1, 112.2,112.3, 112.n, a network 110, and a file system server 102. Thecomponents of the system 100 may be connected directly or over a network110, which may be any suitable network. In various embodiments, one ormore portions of the network 110 may include an ad hoc network, anintranet, an extranet, a virtual private network (VPN), a local areanetwork (LAN), a wireless LAN (WLAN), a wide area network (WAN), awireless WAN (WWAN), a metropolitan area network (MAN), a portion of theInternet, a portion of the Public Switched Telephone Network (PSTN), acellular telephone network, or any other type of network, or acombination of two or more such networks.

The client devices 112.1, 112.2, 112.3, 112.n may be any suitablecomputing device, such as a smart phone, a personal digital assistant, amobile phone, a personal computer, a laptop, a computing tablet, or anyother device suitable for accessing files from the file system server102. The client devices 112.1, 112.2, 112.3, 112.n may access the filesystem server 102 directly, via the network 110, or via a third-partysystem.

The file system server 102 may be any server managing storage and accessto a file system data repository 108. The file system server 102 mayinclude a web server 104, a repository module 106, and a data repository108. The web server 104 may be capable of providing access to the filesystem server 102 over the network 110. In some embodiments, the webserver 104 may be a JAVA web server (e.g., Apache Tomcat). The datarepository 108 may be any storage device capable of storing any numberand type of files organized in any manner using a file system.

The file system repository module 106 may manage and control access tothe data repository 108. The repository module 106 may use lockingmechanism counters to manage file access by keeping track of the numberof client devices accessing any particular file. The counters may keeptrack of writing to files and reading to files in the data repository108. The repository module 106 is described in more detail below.

Although FIG. 1 illustrates a particular example of the arrangement ofclient devices 112.1, 112.2, 112.3, 112.n, a network 110, a file systemserver 102, and components within the file system server 102, thisdisclosure includes any suitable arrangement or configuration of clientdevices 112.1, 112.2, 112.3, 112.n, a network 110, a file system server102, and its components.

FIG. 2 is a block diagram showing example components of a repositorymodule 106 (FIG. 1). In some embodiments, the repository module 106 mayinclude a request module 202, a lock mechanism module 204, and adispatch module 206.

The request module 202 may be configured to receive a request to accessa file node stored in the data repository 108 (FIG. 1). A file node maybe content stored at any particular directory location within the datarepository (e.g., a file, a folder having one or more files, a filereferencing one or more additional files, etc.). A request may be sentusing any web protocol for sending a request over a network and may bereceived at the request module 202 from a client device (e.g., clientdevice 112.1) via the network 110 (FIG. 1). The request module 202 maybe configured to parse a received request to determine information aboutthe file node to be accessed, such as, e.g., the file node specified inthe request (or file nodes specified if the file access request is abatch request), whether the request involves reading or writing to thefile node, etc.

The lock mechanism module 204 may be configured to use the informationparsed from the file access request received at the request module 202to track access to a file node and identify whether the file node to beaccessed is currently being accessed due to another file access request.For example, another client device may be accessing the file nodespecified in the request when the request is received. The lockmechanism module 204 may identify access to a file node by referencing amechanism counter associated with the file node. A lock mechanismcounter may track whether a file node is being accessed and when thataccess is terminated, whether the file node is being read or beingwritten to, the number of client devices accessing the file node, etc.The counter is described in more detail below.

The dispatch module 206 may be configured to provide the client devicewith access to the file node requested if the counter indicates that thefile node is available to be accessed (e.g., the file node is not beingaccessed by another client device). If the file access request is arequest to read a file, the dispatch module 206 may access the file,create a copy of the file, and provide the copy of the file to therequesting client device via the network 110 (FIG. 1). If the fileaccess request is a request to write to a file, the dispatch module 206may provide access to the file via the network 110 so that the file maybe modified and saved in the data repository 108 (FIG. 1).

FIG. 3 is a flow diagram of a method 300 of accessing a file node. In anexample embodiment, the method 300 may be implemented by the repositorymodule 106 included in the system 100 of FIG. 1.

In operation 304 of method 300, the request module 202 (FIG. 2) of therepository module 106 (FIG. 1) receives a file access request from aclient device. The file access request specifies a file node to beaccessed by way of a file system. In some embodiments, the file accessrequest may be a batch request indicating a plurality of file nodes tobe accessed.

In operation 306, the lock mechanism module 204 (FIG. 2) of therepository module 106 (FIG. 1) may reference a counter to identify thatthe file node is being accessed in response to a different file accessrequest. The counter may be any device which stores (and may sometimesdisplay) the number of times a particular event or process has occurred.The locking mechanism counter may indicate whether the file node isbeing accessed by someone else. As discussed above, the counter may beconfigured to track whether the file node is being accessed. If the fileaccess request is a batch request, the lock mechanism module 204 mayreference a counter for each of the file nodes specified in the batchrequest to determine access to each of the file nodes.

In operation 308, the dispatch module 206 (FIG. 2) of the repositorymodule 106 (FIG. 1) may provide access to the file node to the clientdevice when the counter indicates a termination of access to the filenode resulting from the different access request. If the request is abatch request, the dispatch module 206 may provide access to each of thefile nodes as they become available (e.g., when each of the file nodesis no longer being accessed by another client device).

In some embodiments, the counter may be configured to track whether afile is being read or being modified by adjusting (e.g., incrementing ordecrementing) each time the file is accessed. For example, if the fileis not being accessed via a client device, the counter may equal zero.If the file is being modified, the counter may decrement when the fileis accessed for modification such that the counter=−1, indicating thatthe file has a write lock. If the file is being read via a clientdevice, the counter may be incremented when the file is accessed to beread such that the counter=1, indicating that the file has a read lock.In some embodiments, any number of client devices may read the file, andthe counter is incremented each time the file is read. In that case, ifthe counter is greater than zero, the counter may indicate that the fileis being read by one or more client devices, and the counter mayindicate the number of client devices accessing the file (e.g., if thecounter=5, there are five client devices accessing the file based on aread request). In the example described above, the counter isincremented when a file is read and decremented when a file is modified;however, the counter may be adjusted in any manner such that the countermay indicate the status of the file.

FIG. 4 is a flow diagram of a method 400 of reading a file. In anexample embodiment, the method 400 may be implemented by the repositorymodule 106 included in the system 100 of FIG. 1.

In operation 404 of method 400, the request module 202 (FIG. 2) receivesa read file access request from a client device. The read file accessrequest specifies a file to be accessed and read by way of a filesystem.

In some embodiments, a file may not be read if the file is beingmodified by someone else. For example, the file system server 102(FIG. 1) may not allow a file to be read if it is being modified bysomeone else so as to avoid corruption of the file. in operation 406,the lock mechanism module 204 (FIG. 2) may determine whether the file tobe read has a write lock associated with the file (e.g., whether thefile is being modified by someone else). This may be determined byreferencing a lock counter associated with the file. The lock countermay be configured to track whether a file is being modified (e.g.,added, changed, deleted, etc.). For example, in some embodiments, whenthe counter for a particular file has a value of −1, that value mayindicate that the file has a write lock associated with the file. Insome embodiments, any number of client devices may modify a filesimultaneously. In some embodiments, the lock counter may ensure thatthe file is only accessed by one client device during a write operation.When a file is not being modified (e.g., the file has no write lock),the counter may specify a particular value (e.g., counter≧0). When afile is accessed for modification, the counter may be adjusted by thelock mechanism module 204 (FIG. 2) to reflect the modification to thefile and indicate a write lock (e.g., counter=−1). While the exampleprovided indicates that the counter is decremented when the file isbeing modified, the counter can be adjusted in any manner whichindicates the status of the file.

If in operation 406 the lock mechanism module 204 (FIG. 2) referencesthe counter for the file and determines that the file has a write lock(e.g., counter=−1), in operation 408 the lock mechanism module 204 waitsfor a predetermined time period before referencing the counter again(e.g., operation 406) to determine whether access to the file has becomeavailable. This loop may continue until the counter indicates that thefile no longer has a write lock (e.g., access to the file based on theother file access request for modification has terminated; e.g.,counter≧0).

If in operation 406 the lock mechanism module 204 (FIG. 2) referencesthe counter for the file and determines that the file no longer has awrite lock (e.g., counter≧0), in operation 410, the lock mechanismmodule 204 may increase the counter to indicate the file is beingaccessed based on a read request (e.g., counter=1). In some embodiments,if the file access request specifies more than one file to be accessed,the counter for each of the files may be incremented such that eachcounter indicates that the file is being read.

When the counter has been incremented, in operation 412, the file may beread. In some embodiments, the repository module 106 may read the filefrom the data repository 108 (FIG. 1) and create a copy of the file.

In operation 414, the lock mechanism module 204 (FIG. 2) may decreasethe counter to indicate the file access based on that particular fileaccess request has terminated. In operation 416, the copy of the filemay be provided to the requesting client device.

FIG. 5 is a flow diagram of a method 500 of writing to a file (e.g.,modification, deletion, etc.). In an example embodiment, the method 500may be implemented by the repository module 106 included in the system100 of FIG. 1.

In operation 504 of method 500, the request module 202 (FIG. 2) receivesa write file access request from a client device. The write file accessrequest specifies a file to be accessed and modified by way of a filesystem.

In some embodiments, a file may not be modified if the file is beingread or modified by someone else. For example, the file system server102 (FIG. 1) may not allow a file to be accessed and modified if it isbeing read and/or modified by someone else so as to avoid corruption ofthe file. In operation 506, the lock mechanism module 204 (FIG. 2) maydetermine whether the file to be modified has a read and/or a write lockassociated with the file (e.g., whether the file is being modifiedand/or being read by someone else). This may be determined byreferencing the counter associated with the file. As discussed above,the counter tracks access to a file based on a read and/or write accessrequest. For example, the file may have a write lock if the counter=−1,and the file may have a read lock if the counter>0). If there are nolocks on the file (e.g., the file is not being accessed), the countermay equal zero.

If in operation 506 the lock mechanism module 204 (FIG. 2) referencesthe counter and determines that the file is being accessed due toanother file access request (e.g., counter≠0), in operation 508 the lockmechanism module 204 waits for a predetermined time period beforereferencing the counter again (e.g., operation 506) to determine whetheraccess to the file has become available. This loop may continue untilthe counter indicates that the file has become available (e.g., accessto the file based on the other file access request has terminated; e.g.,counter=0).

If in operation 506 the lock mechanism module 204 (FIG. 2) referencesthe counter for the file and determines that the file is no longer beingaccessed due to another file access request (e.g., counter≠0), inoperation 510, the lock mechanism module 204 may decrease counter toindicate the file is being modified and to associate the file with awrite lock (e.g., counter=−1). In some embodiments, if the file accessrequest specifies more than one file to be accessed, the write lock maybe applied to each of the files via a counter associated with each ofthe files.

When the counter has been decremented, in operation 512, the file may bemodified by the client device. Once access to the file has beenterminated, in operation 514, the lock mechanism module 204 (FIG. 2) mayincrease the counter to indicate the file access based on thatparticular file access request has terminated. In operation 516, therepository module 106 may confirm that the write operation wassuccessful by sending a notification of the confirmation to the clientdevice via the network 110 (FIG. 1).

FIG. 6 depicts a block diagram of a machine in the example form of acomputing device 600 within which may be executed a set of instructionsfor causing the machine to perform any one or more of the methodologiesdiscussed herein. In alternative embodiments, the machine operates as astandalone device or may be connected (e.g., networked) to othermachines. In a networked deployment, the machine may operate in thecapacity of a server or a client machine in a server client networkenvironment, or as a peer machine in a peer-to-peer (or distributed)network environment.

The machine is capable of executing a set of instructions (sequential orotherwise) that specify actions to be taken by that machine. Further,while only a single machine is illustrated, the term “machine” shallalso be taken to include any collection of machines that individually orjointly execute a set (or multiple sets) of instructions to perform anyone or more of the methodologies discussed herein.

The example of the computing device 600 includes a processor 602 (e.g.,a central processing unit (CPU), a graphics processing unit (GPU) orboth), a main memory 604 (e.g., random access memory), and static memory606 (e.g., static random-access memory), which communicate with eachother via bus 608. The computing device 600 may further include videodisplay unit 610 (e.g., a plasma display, a liquid crystal display (LCD)or a cathode ray tube (CRT)). The computing device 600 also includes analphanumeric input device 612 (e.g., a keyboard), a user interface (UI)navigation device 614 (e.g., a mouse), a disk drive unit 616, a signalgeneration device 618 (e.g., a speaker), and a network interface device620.

The disk drive unit 616 (a type of non-volatile memory storage) includesa machine-readable medium 622 on which is stored one or more sets ofdata structures and instructions 624 (e.g., software) embodying orutilized by any one or more of the methodologies or functions describedherein. The data structures and instructions 624 may also reside,completely or at least partially, within the main memory 604 and/orwithin the processor 602 during execution thereof by computing device600, with the main memory 604 and processor 602 also constitutingmachine-readable, tangible media.

The data structures and instructions 624 may further be transmitted orreceived over a computer network 650 via network interface device 620utilizing any one of a number of well-known transfer protocols (e.g.,HyperText Transfer Protocol (HTTP)).

Certain embodiments are described herein as including logic or a numberof components, modules, or mechanisms. Modules may constitute eithersoftware modules (e.g., code embodied on a machine-readable medium or ina transmission signal) or hardware modules. A hardware module is atangible unit capable of performing certain operations and may beconfigured or arranged in a certain manner. In example embodiments, oneor more computer systems (e.g., the computing device 600) or one or morehardware modules of a computer system (e.g., a processor 602 or a groupof processors) may be configured by software (e.g., an application orapplication portion) as a hardware module that operates to performcertain operations as described herein.

In various embodiments, a hardware module may be implementedmechanically or electronically. For example, a hardware module maycomprise dedicated circuitry or logic that is permanently configured(e.g., as a special-purpose processor, such as a field programmable gatearray (FPGA) or an application-specific integrated circuit (ASIC)) toperform certain operations. A hardware module may also compriseprogrammable logic or circuitry (e.g., as encompassed within ageneral-purpose processor 602 or other programmable processor) that istemporarily configured by software to perform certain operations. Itwill be appreciated that the decision to implement a hardware modulemechanically, in dedicated and permanently configured circuitry, or intemporarily configured circuitry (e.g., configured by software) may bedriven by cost and time considerations.

Accordingly, the term “hardware module” should be understood toencompass a tangible entity, be that an entity that is physicallyconstructed, permanently configured (e.g., hardwired) or temporarilyconfigured (e.g., programmed) to operate in a certain manner and/or toperform certain operations described herein. Considering embodiments inwhich hardware modules are temporarily configured (e.g., programmed),each of the hardware modules need not be configured or instantiated atany one instance in time. For example, where the hardware modulescomprise a general-purpose processor 602 configured using software, thegeneral-purpose processor 602 may be configured as respective differenthardware modules at different times. Software may accordingly configurea processor 602, for example, to constitute a particular hardware moduleat one instance of time and to constitute a different hardware module ata different instance of time.

Modules can provide information to, and receive information from, othermodules. For example, the described modules may be regarded as beingcommunicatively coupled. Where multiples of such hardware modules existcontemporaneously, communications may be achieved through signaltransmission (e.g., over appropriate circuits and buses) that connectthe modules. In embodiments in which multiple modules are configured orinstantiated at different times, communications between such modules maybe achieved, for example, through the storage and retrieval ofinformation in memory structures to which the multiple modules haveaccess. For example, one module may perform an operation and store theoutput of that operation in a memory device to which it iscommunicatively coupled. A further module may then, at a later time,access the memory device to retrieve and process the stored output.Modules may also initiate communications with input or output devices,and can operate on a resource (e.g., a collection of information).

The various operations of example methods described herein may beperformed, at least partially, by one or more processors 602 that aretemporarily configured (e.g., by software) or permanently configured toperform the relevant operations. Whether temporarily or permanentlyconfigured, such processors 602 may constitute processor-implementedmodules that operate to perform one or more operations or functions. Themodules referred to herein may, in some example embodiments, compriseprocessor-implemented modules.

Similarly, the methods described herein may be at least partiallyprocessor-implemented. For example, at least some of the operations of amethod may be performed by one or more processors 602 orprocessor-implemented modules. The performance of certain of theoperations may be distributed among the one or more processors 602, notonly residing within a single machine, but deployed across a number ofmachines. In some example embodiments, the processors 602 may be locatedin a single location (e.g., within a home environment, an officeenvironment or as a server farm), while in other embodiments theprocessors 602 may be distributed across a number of locations.

While the embodiment(s) is (are) described with reference to variousimplementations and exploitations, it will be understood that theseembodiments are illustrative and that the scope of the embodiment(s) isnot limited to them. In general, techniques for data searches usingcontext information may be implemented with facilities consistent withany hardware system or hardware systems defined herein. Many variations,modifications, additions, and improvements are possible.

Plural instances may be provided for components, operations orstructures described herein as a single instance. Finally, boundariesbetween various components, operations, and data stores are somewhatarbitrary, and particular operations are illustrated in the context ofspecific illustrative configurations. Other allocations of functionalityare envisioned and may fall within the scope of the embodiment(s). Ingeneral, structures and functionality presented as separate componentsin the example configurations may be implemented as a combined structureor component. Similarly, structures and functionality presented as asingle component may be implemented as separate components. These andother variations, modifications, additions, and improvements fall withinthe scope of the embodiment(s).

What is claimed is:
 1. A computer-implemented method operable at aserver, the method comprising: receiving, from a client device, a fileaccess request specifying a file node to be accessed by way of a filesystem; referencing a counter to identify that the file node is beingaccessed in response to a different file access request, the counterbeing configured to track whether the file node is being accessed; andproviding, to the client device, access to the file node when thecounter indicates a termination of access to the file node resultingfrom the different file access request.
 2. The computer-implementedmethod of claim 1, further comprising: if the counter indicates the filenode is being accessed in response to the different file access request,waiting a predetermined amount of time; and after waiting thepredetermined amount of time, referencing the counter to determinewhether the file node is being accessed in response to the differentfile access request.
 3. The computer-implemented method of claim 1,wherein the file access request is a request to read the file node,providing access to the file node including providing a copy of the filenode to the client device.
 4. The computer-implemented method of claim3, further comprising: prior to providing access to the file node,adjusting the counter to indicate the file node is being read; readingthe file node; and adjusting the counter to indicate the access to thefile node resulting from the file access request has terminated, whereinproviding the copy of the file node to the client device is based on thereading of the file node.
 5. The computer-implemented method of claim 1,wherein the file access request is a request to modify the file node. 6.The computer-implemented method of claim 5, further comprising: prior toproviding access to the file node, adjusting the counter to indicate thefile node is being modified by the client device; and after providingaccess to the file node, adjusting the counter to indicate the access tothe file node resulting from the file access request has terminated. 7.The computer-implemented method of claim 1, wherein the counter isconfigured to track whether the file node is being modified.
 8. Thecomputer-implemented method of claim 1, wherein the counter isconfigured to track whether the file node is being read.
 9. Thecomputer-implemented method of claim 1, wherein the file node is a file.10. The computer-implemented method of claim 1, wherein the file node isa folder having one or more files.
 11. The computer-implemented methodof claim 1, wherein the file access request includes a batch accessrequest specifying a plurality of entities to be accessed.
 12. A systemcomprising: a hardware-implemented request module configured to receive,from a client device, a file access request specifying a file node to beaccessed by way of a file system; a hardware-implemented lock mechanismmodule configured to reference a counter to identify that the file nodeis being accessed in response to a different file access request, thecounter being configured to track whether the file node is beingaccessed; and a hardware-implemented dispatch module configured toprovide to the client device access to the file node when the counterindicates a termination of access to the file node resulting from thedifferent file access request.
 13. The system of claim 12, wherein thehardware-implemented lock mechanism module is further configured to waita predetermined amount of time if the counter indicates the file node isbeing accessed in response to the different file access request andreference the counter to determine whether the file node is beingaccessed in response to the different file access request after waitingthe predetermined amount of time.
 14. The system of claim 12, whereinthe file access request is a request to read the file node, thehardware-implemented dispatch module configured to provide a copy of thefile node to the client device.
 15. The system of claim 14, wherein thehardware-implemented lock mechanism module is further configured to:prior to providing access to the file node: adjust the counter toindicate the file node is being read; read the file node; and adjust thecounter to indicate the access to the file node resulting from the fileaccess request has terminated, wherein providing the copy of the filenode to the client device is based on the reading of the file node. 16.The system of claim 12, wherein the file access request is a request tomodify the file node.
 17. The system of claim 16, wherein thehardware-implemented lock mechanism module is further configured toadjust the counter to indicate the file node is being modified by theclient device prior to providing access to the file node and adjust thecounter to indicate the access to the file node resulting from the fileaccess request has terminated after providing access to the file node.18. A machine-readable, tangible storage medium storing instructionswhich, when executed by one or more processors, cause the one or moreprocessors to perform operations, comprising: receiving, from a clientdevice, a file access request specifying a file node to be accessed byway of a file system; referencing a counter to identify that the filenode is being accessed in response to a different file access request,the counter being configured to track whether the file node is beingaccessed; and providing, to the client device, access to the file nodewhen the counter indicates a termination of access to the file noderesulting from the different file access request.
 19. Themachine-readable, tangible storage medium of claim 18, wherein thecounter is configured to track whether the file node is being modifiedor whether the file node is being read.
 20. The machine-readable,tangible storage medium of claim 18, wherein the instructions cause theone or more processors to perform operations, further comprising: if thecounter indicates the file node is being accessed in response to thedifferent file access request, waiting a predetermined amount of time;and after waiting the predetermined amount of time, referencing thecounter to determine whether the file node is being accessed in responseto the different file access request.